Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.94	13.790%	$136.4797	$136.48	$136.50	$136.50
Purchase #2	$36.26	4.290%	$37.8156	$37.82	$37.80	$37.80
Purchase #3	$43.55	6.802%	$46.5123	$46.51	$46.50	$46.50
Purchase #4	$78.61	8.441%	$85.2455	$85.25	$85.25	$85.20
Purchase #5	$216.58	5.240%	$227.9288	$227.93	$227.95	$227.90
Purchase #6	$45.44	5.518%	$47.9474	$47.95	$47.95	$47.90
Purchase #7	$160.75	6.352%	$170.9608	$170.96	$170.95	$171.00
7 purchase totals =	$701.13		$752.8901	$752.90	$752.90	$752.80